NASA bigwigs say that their nuclear powered, laser-packing robotic tank, intended to prowl the ochre plains of Mars, has had its most troublesome bugs ironed out and will be ready to blast off for the red planet next year.
The Mars Science Laboratory - aka "Curiosity" - is a hefty small-truck-sized rover, significantly bigger …

You've missed something allright.

In any project the following happens, a reasonable specification is laid down, and then heavily padded, this isn't padded "victorian style" to add a nice margin in the field. It's actually padded so that the next tier of managers can fel good about whitlling something down, without them cutting into anything important.

Now they're getting so good at the whitlling that they are cheerfully cutting right through the safety margin. They'd spot a simple doubling of design life, so instead the engineers have sneaked "twice the design life" into the testing phase. In practice all this does is increase the wedge on the tail end of the bell curve, rather than actually move the mean that the bell curve is focussed around.

It's called politics dear chap, and it's sadly missing from most undergrad, and even a few grad courses.

Re: Two times design life?

I suspect the design life is designed more along the length of time it will take to carry out it's mission (take X No. of Photos; Carry out Experiments A,B,C.... etc.) rather than just some arbitrary length of time. So the machine is designed to last twice as long as the time it will take to carry out all the tasks required of it. Then there will be a "Nice-to-have" list of things to do after the must-complete list so that they can take advantage of any extra life they get out of it.

Life for space items

When the life of a space item is quoted, it is the life for a given failure prediction (e.g. 99% availability for 3 months). That means that the likely life is a lot longer than minimum design life.

For things that don't wear out, there are standard methods to calculate the likely time to failure, given the level of stress to that part in the design. Normally the maximum level of stress in use is lower than the original part specification.

For things that wear-out, it's different. It the thing doesn't fail but just gets used up like fuel, it's not too hard. But when the wear-out then causes an increasing risk of failure, it gets real hard. So for things like actuators a margin is added to the expected life.

You make it sound difficult

...and that's not acceptable on the 'net.

Everyone knows that anything--particularly tasks involving space travel--can be done rather easily and quickly by any random commenter to any random blog. Just get out of here with your math and calculations and science stuff.

Soon you'll be trying to convince us that private sector companies have to solve the same problems as NASA!

(Evil killer robot dude because I could build a EKRD if I wanted to. I just haven't had a spare weekend.)

@1of10

"Over complex landing system..

too many parts to malfunction on descent... and not taking into account Mars atmospheric conditions."

I *very* strongly doubt JPL puts together a lander without taking local atmospheric conditions into account. It''s those conditions that drove this design. The previous rovers were *tiny* in comparison to this thing so the airbags were a viable option off the shelf for them. This is a beast by comparison.

I suspect JPL management have real issues with in house development of *anything* that is not an actual science instrument. So getting bigger airbags (if you wanted to go that way) or larger landing rockets *developed* as opposed to what is already available, would be awkward. Mars atmosphere is *thin*. The parachute growth curve is *steep*. They grow very fast as mass increases. More creative solutions like "Ballutes" would be both a development project and *untried* . Not something they would bet a multi-billion dollar programme. Put this together and you have a need for a better landing solution using known parts. Hence the skyhook concept. Basically the smaller the mass you have to *completely* decellerate to landing speed the smaller the overall system has to be. What is *not* obvious is that it is the *process* of dropping on those lines that slows the lander. AFAIK if the sky hook does not move sideways it will crash into the ground on *top* of the lander

"Also over complex multi-function analysis arm were everything will be depended on."

there does seem to be a *lot* of shaking and flipping going on. Time will tell if a bit more effort simplifying the motions would have been a better idea.

Historically most of the trouble recently seems to be the inability to choose a system of measurement for the control software and stick to it or (in the case of Stardust) reading a blueprint well enough to install the accelerometer the right way up.

So I imagine this Tank...

It will be interesting to see

how long all those moving parts (lots of mechanical arms, drills, grinders) keep working in the Martian environment.

I'm not so sure that the landing cycle is that much more complex than the "follow the bouncing ball" Spirit and Opportunity landings, but Mars does have a habit of being a graveyard for exploratory missions.

Looking at animations of Curiousity lasering rocks, I have to wonder what a society of inch-tall Martians would make of the vehicle.